
The FL equation is an integrable generalization of the nonlinear Schrödinger (NLS) equation, which is also tightly related with the derivative NLS model. Analogous to the derivation of the Camassa-Holm equation from the KdV equaiton [1]}, the FL equation was initially derived from the NLS equation by utilizing two Hamiltonian operators [2]}. In optics, the FL equation characterizes the higher-order linear and nonlinear optical effects, and has been derived as a suitable model for the femtosecond pulse propagation through single mode optical silica fiber, for which several interesting solutions have been constructed [3]}, [4]}, [5]}.
